Heat exchangers such as condensation-type heat exchangers are required in large numbers, for example for laundry dryers, with such a heat exchanger construction comprising a large number of individual plates which are arranged at a spacing from each other. The plates are held in the assembled condition by a suitable form of holding means. By virtue of their spaced relationship, the plates form between them passages for a first heat exchange medium. Thus for example in a laundry dryer, as indicated above, the process air which has a high level of moisture contained therein is passed through the free spaces between the respective plates. As the plates are hollow, they define hollow spaces extending therethrough, through which for example cooling air is then blown in the context of a laundry dryer. The surfaces of the plates thus form condensation surfaces on which the moisture contained in the air flowing through the passages between the plates is accordingly deposited.
As, from the physics point of view, the transfer of heat from the cooling air side of the heat exchanger has a crucial influence on performance of the heat exchange process, a present arrangement of a heat exchanger, besides the hollow spaces referred to above, which are smooth, additionally has small strips of aluminium sheet which are secured in position as by glueing, thus giving additional heat exchange surfaces. Although the fact that the additional heat exchange surfaces are glued in position on the cooling side of the heat exchanger increases the level of efficiency thereof, that does however give rise to the consideration that the strips have to be stuck in position, which is a disadvantage from the manufacturing process point of view. Furthermore, the heat dissipation effect of such additional heat exchange surface portions is also checked or obstructed at the adhesive joins so that, in the present state of the adhesive art, it is necessary to glue a very large number of additional heat exchange surface portions in position in the heat exchanger arrangement. That in turn results in a high level of induced flow resistance, whereby the danger of clogging due to impurities and contaminatory material in the cooling air, which cannot be dissipated, is substantially increased. Over a service life of at least ten years, it is not impossible that the adhesive joins would have to be changed.